Towing a travel trailer or 5th wheel trailer is a common practice, but did you ever consider how towing a trailer affects the tow vehicle’s power-train?
The best place to start is explaining what a vehicle’s power-train is
The power-train on a rear-wheel-drive vehicle includes every component required to get the power from the engine to the rear axle and the vehicle’s rear wheels. The vehicle’s engine is rated in horsepower and torque. To get that torque to the vehicle’s rear wheels, it must first go through several components in the vehicle’s power-train.
First, the power leaving the engine goes to the transmission. In this case it’s an automatic transmission. The transmission provides a variety of gear ranges, based on the speed and torque for the driving conditions.
Most modern-day vehicle’s used for towing or hauling heavy loads have a tow/haul transmission mode. If you are towing, and the transmission keeps shifting in and out of gears, you can use the tow/haul mode. Read your owner’s manual for more information on tow/haul and gear selection when towing.
From the transmission, the power is delivered to the rear axle by way of the driveshaft. From there, the axle uses a pinion and ring gear to get the power to both rear wheels. Axles come with different gear sets, which is typically referred to as the axle ratio. The axle ratio is a comparison of how many times the drive shaft rotates in relationship to how many times the rear wheels rotate.
Axle ratios are expressed in numeric values. For example, a 3.73 to 1 ratio means the drive shaft, or pinion gear rotates 3.73 times for each rotation of the rear wheels, or the ring gear. The lower the numeric value is (3.21:1) the better the axle is for fuel economy, and the higher the numeric value is (4.10:1) the better the axle is for towing.
Under normal driving conditions all of these components do their individual jobs with very little stress, and with operating temperatures in the normal ranges. When you add additional weight to the vehicle, like a travel trailer or 5th wheel trailer, the components I just discussed are expected to do the same job as before, with the added weight and stress on the power-train components.
Let’s see what happens under this scenario
With additional weight, comes more heat and friction as the drive-line does its job. When the coolant, oil and fluids run hotter than normal its more difficult to lubricate the metal on metal components, causing increased friction and wear.
This is why truck manufacturers offer towing package options. To counter the effects of the added stress, and optimize towing, tow packages offer components like a heavy-duty cooling system, engine oil coolers and transmission coolers, upgraded suspension system, larger brakes, built-in trailer brake controller and towing mirrors.
And when you use the proper hitch components, like a weight distributing hitch, it helps lessens the stress on the power-train when you are towing a trailer. So, it is easy to see how a towing package is designed to help deal with the added heat and stress placed on the vehicle’s power train.
But, possibly the most important thing we as tow vehicle owners can do is make sure the engine coolant, engine oil, fluids and all filters are replaced on a regular schedule. Fresh oil, fluids and filters provide the highest degree of lubrication qualities, and are the best defense against heat, friction and stress on power- train components when you are towing a trailer.
Mark J. Polk
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